If anyone can help with the following is really appreciate it... I'm a bit stuck as to where to find advice on this!?

I'm traveling back to the UK in January and I've got a direct flight from Bangkok booked. I live in Cambodia and will fly from Phnom penh to Bangkok and then to go through immigration and check in for my new flight in Bangkok.

Has anyone done anything like this recently, I used to do it all the time but I'm just not sure of the rules on this right now? I will be in the country for a maximum of about 12hrs, I won't be leaving the airport but I will have to go through immigration to collect my luggage and check in again.