the problem is, you actually cannot make a multi-entry visa invalid. You have to wait until it expires, before an embassy would allow you to apply to a new visa. You cannot hold two different visa at the same time. . . . Neither Immigration nor the Thai Embassy has the right to void an METV any day earlier before it officially expires
you also need to consider timing the date of the yearly applications to a new "retirement extension". Example: If you enter with a Non-Imm-O visa on December 10, the date your extensions end will be March 9 every year - and you must be present for that. . . . in case the embassy refuses to issue a 90-days Non-O visa, because you are on a still valid METV, the earliest date you can enter Thailand with a fresh Non-O visa would be beginning of March. This would shift the date of yearly applications to the 1-year extensions to the beginning of June. You would need your presence in Thailand in the hottest month and probabyl also a very wet month.
it could be a problem that you still have a valid visa until February. Normally, one cannot apply for a new visa unless a valid stay permit or valid visa has been made invalid prior to applying for new visa
Including medical expenses, lost baggage, and travel delays, generally begins on the day you depart. This start date should match your actual departure date as listed on your itinerary. It's important to ensure that your insurance policy reflects the correct start date to avoid any gaps in cover.
it is amazing that you openly advertise for a 10-days tantric seminar on Phi Phi in May by next year, for which you never ever would get a work permit in Thailand. In other words - you are already putting yourself at risk, long before your plans have worked out
sorry to burst your bubble. If you are "caught out on overstay" somewhere else in Thailand - meaning you are not already at the airport on your way out of Thailand = which is described as "surrendering to the authorities" - you will get arrested, put into the detention center, forced to buy a one-way ticket out on your expenses and you will be banned to enter Thailand for 5 years (if the overstay was for less than one year) It is CLEARLY posted