I'm here on a retirement extension and have two trips this month.

Will depart for trip 1 with a re-entry permit in passport A.

Can I return from trip 1 and enter visa-exempt on passport B, leave on passport B and then return from trip 2 on Passport A with the re-entry permit?

I'm guessing worst case is that VE might be declined and then will have to use the RE permit?

It's not a big deal either way, just looking to save a little time and money.

This is a very good way to get pulled into an interrogation room and questioned about what you are doing and why you are playing games with your passports.  All to save 1000 baht?  Doesn't seem worth the risk.  Even people just normally changing passports betwen trips get questioned often enough, but you are planning on doing it 2 times in short order.

Try it and tell us what happens. You aren't breaking any rules. It is really a cheeky thing by charging us 3800 a year for entry permits on a valid visa. Have you ever asked your immigration officer?

8 hours ago, Two Plus Two said:

I'm guessing worst case is that VE might be declined and then will have to use the RE permit?

Seriously?

In future buy a multiple reentry permit 3800b.

You can even splurge and pay 200b for immigration at airport to fill in the TM8 and provide photo. 

Also be aware that flying visa exempt the airline at departure may wish to see onward flight. 

Poor plan..

Sounds to me that you are really trying to avoid staying more than 180 days a year in Thailand.  It won't work.

Thanks all for your thoughtful replies.

For the avoidance of angst I'll just go with re-entries.

As it happens, I attended the immigration office to renew my extension this morning and they, as I kind of expected, said I shouldn't take the VE route.