One more caution: asking rent is not necessarily achieved rent. If those units have been advertised for a while, the apparent gap may overstate what a replacement tenant would actually pay. Vacancy time matters just as much as the headline number.
A few missing details could change the answer. When does the current lease end, is the apartment furnished, and has the owner had to spend much on maintenance during this tenancy? Also, is THB 86,180 based on genuinely comparable units in the same building or just broadly similar Bangkok listings?