Where to go, few days in May/June

Parks like Khao Yai and Kaeng krachan are within short distance (for Thai standards... about 3 hrs drive).
And these are some of the best parks in the country for wildlife watching. Though, if you go by yourself and have no experience in the jungle, it could still be a challenge to find the animals.

These are not stupid questions.
The best way to go is with an experienced guide, but maybe I am prejudiced ;-)
For general wildlife tours, you will find most offers for Khao Yai.
Simply google 'Khao Yai tours' and you will find various options.
For Kaeng Krachan there are not much offers apart from bird watching trips.

About time of year, May-June should be fine. For mammals I don't see much difference throughout the year. Birdlife varies depending on migration and nesting season. But this period should be OK for birdlife. And for reptiles too.

Looking forward to seeing some of those pics!! Khao Yai is another place I have not had time to go to for a while and I love to see what I am missing ;+)

Sounds like you had a good trip. Yes, the daily feeding migration of the Wrinkle-lipped Bats is amazing indeed. I have seen it many times, but still each time it is unbelievable to see that for one hour long! bats keep flowing out of the mountain, non-stop. I have never been inside the cave, but it must be huge.

You need a bit of luck when visiting that the wind direction is good (on departure they fly against the wind) and that the bats come out not too late. The earliest I have seen them come out was at 16:30, sometimes they wait till 19:00 before they start, but generally it is around 17:30 - 18:30...
With Southwestern wind is nice because you can photograph the swirling river of bats against the sunset background, and often in that time of year they come out relatively early and often seem to fly very low. So low that you can nearly touch them while standing on the ground.
Indeed a must to see for those who haven't seen it yet.

Glad to hear Jay & Tata did a good job.

How was the weather, was it rainy that the birds did not really want to show much?
I agree with Paul (admin), show us some pics ;-)

Nice shots on your 500px account. Looking forward to see more!
Very lucky to get the shot of the elephant bading in the river. I have seen a lot of elephants in Khao Yai, but only a couple of times in the water.