Welcome back to Phuket! I'm going "home" Phuket from Vientiane Friday. 😊 Yes stamp passport at BKK. Unsure ask ground staff they will point to direct you. Most probably like how we reached Laos, go thru luggage claim and enter "sad escalator" onto domestic terminal again. Out & in again 😊 I have 3hour layover. I check most flights have 3 to 4hours layover hope you have enough time. Safe trip back! 😁