What do I need to travel to Cambodia on a retirement visa that expires in 2018?

Only if you have or get the re-entry permit.

Colin, if you only paid 1.900 Thb for the stamp Expire /2018 you need to go back to Immigration or visit the booth on the airport BEFORE leaving Thailand. You need a Re-Entry Permit (as shown on the picture before), on return they will stamp you in till /2018. Without re-entry permit you LOOSE your stay in Thailand and need a NEW visa from a Thai Embassy or Consulate.

if you don't have a re-entry permit you'd need to buy one and like

@Rob***

, said, they're 1000baht for a single or 3800baht for a multiple, you get it at the immigration office or at the airport when you fly out.

Thanks, than it is the procedure as I posted about Extension of Stay.

@Co***

, a stamp similar like this is the last current one in your passport with the date in 2018?

Okay, first off we need to find out what you exactly have

@Co***

, :/

Do you have a VISA stamped in your passport from a thai consulate

OR

Do you have a yearly extension of stay you got at the thai immigration office.

Or if you have an O-A you'll get another year.

If you are on an Extension of Stay based on retirement, you need a re-entry permit before leaving Thailand. You can buy at Local Immigration office 1000 Thb for Single re-entry or 3800 Thb for multiple re-entry. Or return you will get the same date as admitted to stay as the day of your Extension of Stay. If you are in Thailand with a Non O visa with multiple entry and enter before date ../../2018 as long as you enter before that date you will get 90 days admitted to stay when entering Thailand. Long answer but at least tried to explain both, just because it is not clear what stamp or visa is in your passport.

Make reentry