When in the US we're in the Boston area. The New York Thai Embassy comes to Boston twice yearly to serve the Thai expat community. But Thailand being a wealthy nation, we certainly can't expect similar service from the impoverished US Embassy in Bangkok ????
The older I get the more likely I am to pay for extra service, be it Business Class seats, VIP arrival service, or agents to make dealing with bureaucrats easier.
I'd definitely use an agent to help with a passport renewal if offered.