I am not sure what its proper name is but the kind of visa for 30 days stay (or visa exemption I think its called) that you get when arriving by air

Is there a limitation on how many times one can get that?

Thanks

No! Unlimited afaik.

That is a visa exempt entry. No, there is no limit. Only by air will you get 30 days, by land only 15. Note that the airline might require you to show proof ( a ticket out) that you will leave Thailand within those 30 days.

Great thanks

Anyone done a visa run to Phnom Penh from Bangkok? Do you need a visa when arriving in Cambodia or can you get back without having to go through Cambodian immigration?

How likely is it to get asked for a ticket out of Thailand? 10%, 50/50, an educated guess will do...

Thanks

You need a visa and you have to pass through immigration. It can be obtained at the border. No ticket is required.