What are the requirements and implications for volunteering in Thailand on a retirement visa?

I am hoping someone can assist me with some questions I cant seem to get clarification on.

FACTS...

*Arriving in Samui on 5th March 2019

*Hoping to stay as long as physically possible (three years min)

*Partner going on retirement visa

*I plan to do vol work and have received paperwork from vol org already

Questions... I want to take a few days to settle first (for myself and my partner and two cats (yes they are already sorted).

a. filling in the paperwork for visa, should my start date be the date I arrive or the date I plan to start vol work?

b. vol paperwork... should it state vol work date for a year or the ninety days that the visa says

c. do I still do the regular visa run

d. what happens when the visa expires? is it a standard visa run and recompleting paperwork or do I have to vacate entirely and start again

any advice would be greatly appreciated <3