I have a 60-day single entry Thai tourist visa which I obtained in Vientiane, Laos. I am currently in Cambodia and thinking I might stay here a bit longer than the one month I have. With my planned itinerary it might not be too much effort to pop over the border at Poipet/Aranyapathet and return to get a new 30 day Cambodian visa.

However, I don't particularly want to waste my 60 day Thai tourist visa on a border run from Cambodia. Will the Thais leave my visa alone and stamp me in for 15 days if I ask, so that I can use the 60 day visa later?

You can ask, some officers seem more willing to help than others.

As has been said, ask politely and explain but do not expect to be granted your wish. Sometimes they will allow it, sometimes not.

I know where I would bet my money on to be totally honest.

as far as I know you can extend your Cambodia 1month Tourist Visa once for another 1month.

Ask and you should receive. I don't see any problems with obtaining a 15 land or 30 day air visitor visa at any Thai crossing. I've personally done it a handful of times. Border officials are very nice and done to earth. I have nothing to say about US Customs and Immigration who will refuse entry on a twitter feed. Have fun and keep us posted.

as far as I know you can extend your Cambodia 1month Tourist Visa once for another 1month.

Yes, according to http://www.cambodia-travel.com/information/cambodia-visa.htm

Visa Extension

• Travelers who would like to prolong their stay in Cambodia may extend their visa at the Department of Immigration situated just opposite the Pochentong Airport. The visa may be extended for 30 days at the cost of USD 25.-
  

I tried it last year when I flew into Bangkok but immigration wouldn't entertain the idea. At the time I only wanted to stay in Thailand for about 1 week before going to Cambodia, so I didn't want to waste the double entry visa i had in my passport.

I tried asking them to just stamp me in for 30 days and ignore the visa, but no, the visa got activated. The woman didn't even listen to me.

But it's worth giving it a go, you might catch one of them on a good day.

I tried it last year when I flew into Bangkok but immigration wouldn't entertain the idea. At the time I only wanted to stay in Thailand for about 1 week before going to Cambodia, so I didn't want to waste the double entry visa i had in my passport.

I tried asking them to just stamp me in for 30 days and ignore the visa, but no, the visa got activated. The woman didn't even listen to me.

But it's worth giving it a go, you might catch one of them on a good day.

There's an appearance factor clause. If you look like the Ya Ma ( medicine for horses ) addict you can forget getting any slide. Show respect, greet in Thai, smile and be professional. Best regards.

Actually it appeared to be more of a policy decision as there were a number of such reports in short order (previously such a request was normally accepted). Have seen several more recent allowances so perhaps another change of heart and will worth asking. But no guarantee even on best behavior.

Yes you can do

I tried it last year when I flew into Bangkok but immigration wouldn't entertain the idea. At the time I only wanted to stay in Thailand for about 1 week before going to Cambodia, so I didn't want to waste the double entry visa i had in my passport.

I tried asking them to just stamp me in for 30 days and ignore the visa, but no, the visa got activated. The woman didn't even listen to me.

But it's worth giving it a go, you might catch one of them on a good day.

This was my experience. I was crossing the border at Poipet/Aranyaprathet. To be honest I think I would have just got the stamp had I just presented my passport and said nothing. But I asked, and the border guard went off to get someone higher up, and the answer was no. So complete waste of a 60 day visa in a 3 day trip to Thailand. You can get a reentry permit at the airport for I think 1,000 baht- I think this allows you use the remaining days on your visa and may make sense if they 'stop the clock' when you leave (not sure on that.)

They do not stop the clock - you will be stamped in for your previous permitted to stay date using a re-entry permit. But it makes sense for many people.

Two years ago I got away with it by not saying anything and also on the entry form there is a visa section I didn't fill out. Last year the officer saw the visa so I explained politely that I would only be there for a few days before leaving and then return a week later. He called his boss ove and after much discussion the boss said no. He said I could get a re-entry permit when I left if I wanted but I had to use the visa.

I tried it last year when I flew into Bangkok but immigration wouldn't entertain the idea. At the time I only wanted to stay in Thailand for about 1 week before going to Cambodia, so I didn't want to waste the double entry visa i had in my passport.

I tried asking them to just stamp me in for 30 days and ignore the visa, but no, the visa got activated. The woman didn't even listen to me.

But it's worth giving it a go, you might catch one of them on a good day.

This was my experience. I was crossing the border at Poipet/Aranyaprathet. To be honest I think I would have just got the stamp had I just presented my passport and said nothing. But I asked, and the border guard went off to get someone higher up, and the answer was no. So complete waste of a 60 day visa in a 3 day trip to Thailand. You can get a reentry permit at the airport for I think 1,000 baht- I think this allows you use the remaining days on your visa and may make sense if they 'stop the clock' when you leave (not sure on that.)

In the end it is called better planning, planning your stays to best use your visas.

They do not stop the clock - you will be stamped in for your previous permitted to stay date using a re-entry permit. But it makes sense for many people.

Right, would not have made any sense in that case as I was away for 28 and got 30 days when coming back anyway.

the end it is called better planning, planning your stays to best use your visas.

Good on you Moe, hope you never change your plans or do anything spontaneous, might give you too much of a shock there.