The All Whites started the same eleven that drew with China, but after 30 minutes they had a midfield reshuffle as Marco Rojas was replaced by Tim Payne and Michael McGlinchey was pushed further forward. The changes coincided with New Zealand's structure falling apart.
The last 15 minutes of the first half was dominated by Thailand, and they deservedly went in front just before halftime, when a misdirected shot landed at the feet of Kirati Keawsombut who lashed it home from the edge of the box.
Kosta Barbarouses had New Zealand's best chance of the first half when he blazed high over the bar from the penalty spot, after some nice hold up work from Chris Wood.
The Melbourne Victory striker has only scored two goals in 25 games for the All Whites, and his current form in front of goal will not be making Anthony Hudson's life any easier.
Chris Wood also had an off night, missing a host of good chances, and Hudson must wonder where the goals will come from if his main attacking weapon isn't firing.
Striker Jeremy Brockie (one goal in 45 games) replaced Barbarouses at halftime and had an immediate chance to equalise but he dragged his close range volley went well wide.
The game stretched as New Zealand went searching for an equaliser and when attackers Kayne Vincent and Tyler Boyd joined Brockie, Wood and Ryan Thomas up front, the defensive cupboard was left very bare.
Thailand capitalised when New Zealand goalkeeper Jake Gleeson spilled a long range shot and Kraison Panjaroen was on hand to tuck home the follow up.
It was a disappointing way to end the tour for Gleeson, who had earlier pulled off a number of acrobatic saves and generally looked strong and composed.
In the last ten minutes Thailand rattled the cross bar and had a volley cleared off the line by Tim Payne as New Zealand poured forward in droves, searching for a late miracle.
Thomas was New Zealand's best, with a number of clever step overs, through balls and dribbles, while Tommy Smith let his frustrations boil in the dying stages as he was booked for dissent.
After such a positive, promising performance against China, today's result will leave a bad taste in the mouth for Hudson and his management team who now take two steps back and try to figure out where it all went wrong.
"Tonight was a disappointing result for sure," said Hudson.
"Tonight I saw a lot of things where I know we can build on. If we came here tonight and didn't create chances and have those good periods I would have been disappointed.
"But this is the reality now, we have come into the changing room and we have to understand that there were certain areas of the game that were not good enough.
"What we do know is we have a really good group of players. A lot of the group lacks experience but we have to quickly learn and step up to the plate. We will deal with it and we will get it right."
