I just completed the LTR pensioner, went seamless. A few things to note; first there are some posts that say you can pay various ways. There are only two, cash or Thai bank transfer, that's it. You're at Chomchuri Square and pay at the same Immigration window everyone else does.
The second thing, it reads as if you get a work permit with the LTR visa, you don't. You're just eligible to get one via the BOI-LTR online system and you don't count as a foreign employee. You still have to have a registered Thai company hire/sponsor you. Spare the Mods and post any questions about WP's to the appropriate forums. I don't have anymore information anyway.
Process takes 1-1.5 hours, maybe less. However, if you have the 11-12 appointment slot you may have to come back after lunch. Like all other visa's, after the nice people at the BOI do there thing, the completed docs go to immigration for review and final approval, this can take some time. The last part as always is pay your fee then turn in you're visa application and passport at the Immigration window to be stamped. The only difference is you don't have to Que:)
I'm not including BOI steps here because it will vari and you will have someone assist you start to finish including walking thru the Immigration office and an out-brief when your done.
Good luck all.
