almost all record/video bars in Bangkok sell both R1 and R3 DVDs......
here's some of my fave spots....
MBK mall
a) 4th floor DVD store (can't remember the name sorry)-it's on the corner nearest the BTS station(as in dulong dulo, beside p-dvd shops)...they have Region 1's on the left side and R3's on the right...properly labeld naman racks... a little pricey for the R1s though...1000-1500 baht.....same week released sa US ang title nagkakaroon sila...
b)Video store at the 3rd floor malapit sa escalators...the name of the store is in Thai....mostly VHS rentals....and the R1 dvds are very limited and placed on a 4X7 shelf...1 copy lang per title and for new releases lang....
pero kung makaka-tiyempo ka...this is where the cheapest dvd can be found...iyong shrek (2 disc coll ed ata yon)nga di ko nabili non kasi di ko pa siya napapanood...900baht lang....iyong classic cartoon na "grinch" nabili ko rito for 700baht...
c) R3 video store sa 2nd floor(o 3rd ata).....
Central Mall at Central Ladprao(near Sofitel hotel)
may R1 and R3 shops sa dulo ng 3rd or 2nd floor ata yon
World Trade Center....(english name shops)
2 shops for R1 and R3 malapit sa stairs sa 2nd floor...
1 video rental shop(me LD pa) at the same level sells ex-rental R1 dvds as low as 500baht....
almost lahat ng malls me video shop .....
eto lang naalala ko..... hope it helps....