My kids will travel alone to Phuket soon from UK though Bangkok. Their bags cannot be checked through to Phuket and so they will need to collect bags and then check in for the domestic flight (still at Suvarnabhumi Airport).

 

 Is this an easy enough process? Would they pass through immigration in BKK and then proceed to domestic area with bags or what?  Anything to watch out for? Grateful for advice.

port of entrance being Bangkok thus immigration will be done there... they need to remove their luggage and carry it to the domestic terminal but not a big deal as there are escalators from one floor to the other

International arrivals are on the ground floor, they have to collect their luggage then head to leve four check in to connect to their destination flight. Escalators work all the way up. Easy process

Same as any other airport. Follow the signs.

If your kids are unable to get from International to domestic terminals on their own, they really shouldn't be travelling alone