How long can I stay in Thailand with a METV before I need to re-enter for my third entry?

As

@Liam ****

(and others) correctly pointed out the "enter before" or

"must be utilized by" date on the VISA itself controls whether you can get another entry out of it or not.

It is an unlimited entry visa for its validity (6 months from the date it's issued) meaning you could exit/re-enter the country every day for the validity of the visa if you wanted to and you'd get stamped in for 60 days.

Here's an example. This 6 month METV from Kuala Lumpur has an enter before date of 8th Feb 2018. As long as the holder of that visa entered the country on or before that date they would get stamped in for 60 more days.

So look on your visa and see what the "enter before" date is. IF you can get back to thailand on or before that date you'll get stamped in for 60 more days, if you can't you should get a new visa before you come here.

@Stéfan *******

, sorry I deleted your comment about the 180 days in a year "rule"..

There is NO official rule about how many days you can stay inside thailand on visa exempt or tourist visas in a specified time period.

I know many many people who have had 6 month METV's and who have gotten almost 9 months of stay out of them by bouncing out&back in every 60 days and extending their last 60 day entry by 30 more days.

Your METV will say "must be utilised before" and then a date stamped on it, so even if you stamp in 1 day before that date, you will be stamped in for 60 days. That date will be 6 months from the day you are granted the visa, so you can come and go as much as you like within that period.

There is an enter before date when it's issued enter before then and you get your 60 days

The METV is valid for 6 months from the date of issue.