Built a lot, dept stores and malls have parking. Would more parking lots solve the traffic problem in BKK? Of course not. Otherwise, more would have been built, cheap "solution." Los Angeles tried it. How'd that work?
BKK also has the taxi fleet, buses, BTS, and MRT. Neither all that transport NOR the stopping of cars and bikes parking anywhere they want ever solved the traffic problem.
And Thais do quite a bit of walking to and from stops and stations. In the tropical heat of Thailand, walking isn't the experience it is in northern climes, BTW. Most foreigners are ALSO quite happy to take the BTS (or baht bus in Pattaya) to avoid walking in that heat as well. They drive their cars and bikes same as Thais, if they have them.
The better the infrastructure (not just transport), the greater the economic growth and the larger the population taking advantage of it and supporting it. Central Festival (or CP) helped pay for an upgrade to the electric grid to make the mall possible. The mall helped bring in a lot more tourists and traffic to Pattaya, even though it has a parking lot. The festivals started up to cash in. The road needed widening . . . .
So it has been in Pattaya, even with its limited development. That's why implementing your idea would make little difference in the long run, just as it hasn't in BKK.