From the BOI site, it does appear that you are only required to show an income of at least USD80k for two years prior to applying, if taking the "passive income" route. Then, I assume, you'd need to do the same for your 5 year extension. So two years prior, and years three and four would need this income if that is the case.
Required-Documents-for-Qualification-Endorsement-for-Wealthy-pensioner-16-03-66.pdf (boi.go.th)