@Terrance ******
There are 2 types of trips. Border bounce and visa run. Most agencies do border bounces where they just take you to the border, stamp out and immediately stamp back into Thailand, and return to where you were picked up. That's not what you need.
So in your research make sure you find an agency that specifically does visa runs, to apply for a visa in another country. Almost all of them go to Laos because both of the Thai consulates in Laos are on the Thai/Laos border.