Is there a website with central access to the bus schedules around the country?

Crossing over from Laos to Thailand at the friendship bridge at Mukdahan.

1) Is there a bus or a tuk tuk once on the Thai side to get me to Mukdahan bus station then to BKK?

2) How early, should I get to Mukdahan bus station trying to catch the earliest bus to BKK since it’s a 12 hr Journey …Is there a bus leaving for BKK once or twice a day (schedule)? I Try checking 12GoAsia but nothing showed up. Planning to cross the border on April 20.

TIA

Newly updated bus times. Ekkamai to Pattaya, and Mo Chit to Pattaya (and vice versa) will be the primary image, and I'll also put Suvarnabhumi to Pattaya and Pattaya to Hua Hin in the comments.

There is a bus every hour from Ekkamai to Pattaya from 6:00-21:00. The specific times shown in the image are buses that you can purchase tickets for ahead of time from the website.

There is also a bus every hour from Pattaya to Ekkamai from 4:30-21:00 and the times shown are buses you can purchase tickets for ahead of time.

Top left is Ekkamai to Pattaya, top right is Pattaya to Ekkamai.

Bottom left is Mo Chit to Pattaya, bottom right is Pattaya to Mo Chit.

Prices are 138₿ for all routes shown in this image.

Reservations can be made www.rrcticket.com

During holidays and other busy times, there will be buses every 20-30 minutes.

Also there are almost always mini-buses (vans) going from Ekkamai to Pattaya and Pattaya to Ekkamai as well. They depart when they have enough passengers to be full.

Anyone know how much time we need for the Mae Sai run to go out and come back in? I have around 1-1.5 hrs between b uses. Is that enough time? or should I change my schedule to allow for more time while I still can?