The international-to-international transfer process on CA at PEK T3 is abbreviated--you need to deplane, walk (fast) to Immigration area and use the International Transfer corridor to get to security checkpoint and back to airside. There will not be a formal Immigration process to pass through, and you will not need to claim Baggage, it should be tagged through and routed to BKK. If you do not get the PEK-BKK boarding pass beforehand, then you'll need to stop by the Airline Transfer desk which is before the Immigration area, and get them to issue this or you can't get back airside. Assuming the 19:45 departure is not delayed, they'll last call for boarding the BKK flight around 19:30. So you have less than 65 minutes.

If the flight in from JFK is bang on time at PEK, you might make it. The problem is that on-time arrival doesn't happen too often on this flight. So you need to contingency plan for the misconnect and have suggestions for rebooking to give to CA staff--they aren't necessarily that proactive or creative. Fortunately mid-November travel is not all that busy so there should be seats on some sort of combination to get to BKK but earliest you'd arrive would be next morning. Remember you'll cross date line and arrive at PEK evening of 11/16. IMO, best options to play for Plan B's are in order of preference:
1) TG nonstop flight departing 11/17 05:55 arr BKK 10:10.
2) CA midnight flight to SIN dep 00:10 arr 06:30 connect TG dep 08:15 arr BKK 09:35.
3) CA evening flight to HKG dep 21:00 arr 00:40 connect TG dep 07:50 arr BKK 09:35.

CA's preference will be to book you on their own metal but they can usually be persuaded to put you on some of the Star Alliance carriers. Non *A options, probably won't have any luck but there's not a lot of advantage on timing or convenience with those anyway--all would require connections somewhere. This sort of rebooking will be done out at the main desks on the nonsecure side of the terminal, so in the event of a misconnect, you'll be directed to go through Immigration (Transit without Visa if you have no Chinese visa) instead of the International Transfer Corridor, and then get your bags at Bag Claim, which will be offloaded from the flight you misconnected. Then deal with CA desk.