Will I encounter any problems upon returning to Thailand after a border run in Cambodia?

Really depends on your entry history to Thailand. If it’s your only border bounce then almost certainly no issue. If you have a series of previous entries and/or covid extensions then almost certainly you could have issues.

If questioned by immigration on arrival you need to provide 3 proofs for entry into Thailand.

1. 20,000 baht cash or equivalent in a major currency. It needs to be in cash. A bank statement, credit card or phone app showing you have funds won’t suffice.

2. Accommodation booked for at least the first few days. If you’re staying with family or friends then have them write an invitation letter for you to stay at their place.

3. A ticket out of Thailand booked within the number of days your entry allows, regardless that you can get an in country extension. 30 for Exempt, 60 for Tourist Visa (although the likelihood on being asked if you have a actual tourist visa is minimal). Bus train or plane. The two former must be an international ticket out, not just to a border town where you could walk across a border.

These proofs won’t guarantee you entry as that’s at the discretion of the immigration officer, but they’re the three things they’ll generally use as a reason to deny entry.

Nothing is ever 100% certain but usually there is no problems as long as you didn’t do anything to get the red stamp in your passport prior to departure from Thailand…