Use the men with the long tail ,they will assist you thru the immigration,cost 500 baht for the boat, ,take you to Ranong , wait and ring you back.you’ll need 10$ US for the Myanmar immigration,Can pick up some duty free there across the road, Beware of the many locals trying to sell you stuff. The 20,000 baht may on your not be asked for because they know you’re coming from Thailand doing a visa run.