the rule is if u have 12 hours plus in BKK transit u need a visa, and u will need to goto the Thai embassy since Nepali passport cant get u a visa in the airport... i had 13 hour transit in BKK and i didnt need a visa..but it gave me some tension.... the travel agents will all tell u , u need visa for more than 12 hours in bangkok. BUT u have 4 hour transit.. u have nothig to worry about... just go relax..and catch ur next flight.. -lato