Box Office Thailand for May 21–24, 2009
| TW | LW | Movie | Studio | Weekend Gross | Change | Screens | Change /Avg. | Gross-to-Date | Week | Production Country |
|
| 1 | N | Night at the Museum: Battle of the Smithsonian | Fox | $655,956 | - | 160 | - | $4,100 | $926,462 | 1 | Unknown |
| 2 | 1 | Angels & Demons | Sony | $280,151 | -59.7% | 70 | - | $4,002 | $1,164,041 | 2 | Unknown |
| 3 | 2 | Saranae Haw Peng | Mongkol Films | $68,315 | -67.0% | 60 | -15 | $1,139 | $2,582,388 | 4 | Unknown |
| 4 | 3 | Star Trek | UIP | $57,731 | -59.8% | 64 | -21 | $902 | $779,877 | 3 | USA |
| 5 | N | Krasue Fud Pop | n/a | $28,336 | - | 50 | - | $567 | $28,336 | 1 | Unknown |
| 6 | 4 | X-Men Origins: Wolverine | Fox | $20,948 | -70.0% | 48 | -30 | $436 | $2,292,994 | 4 | USA |
| 7 | N | Rule Number One | Mongkol Major | $8,101 | - | 15 | - | $540 | $8,101 | 1 | Unknown |
| 8 | N | Righteous Kill | n/a | $5,193 | - | 1 | - | $5,193 | $5,193 | 1 | USA |
| 9 | 8 | Thick as Thieves | n/a | $3,274 | -38.8% | 4 | +2 | $819 | $27,231 | 3 | USA |
| 10 | 5 | Mor 3 Pee 4 rao rak nai | RS | $2,502 | -90.0% | 15 | -29 | $167 | $561,983 | 4 | Unknown |
| 11 | 9 | Winged Creatures | n/a | $1,980 | -20.8% | 1 | - | $1,980 | $5,819 | 2 | USA |
| 12 | 13 | Ssanghwajeom (A Frozen Flower) | Mongkol Major | $1,091 | -13.5% | 1 | - | $1,091 | $59,952 | 6 | South Korea |
| 13 | 12 | The International | Sony | $1,084 | -25.7% | 1 | -1 | $1,084 | $55,943 | 6 | Germany, UK, USA |
| 14 | 6 | The Horsemen | Mongkol Major | $547 | -95.0% | 5 | -31 | $109 | $96,919 | 3 | USA |
| 15 | 17 | The Great Buck Howard | Mongkol Major | $379 | +86.7% | 1 | - | $379 | $17,085 | 9 | USA |
| 16 | 14 | The Haunting in Connecticut | Mongkol Major | $334 | -72.0% | 2 | -2 | $167 | $412,693 | 5 | USA |
| 17 | 15 | Slumdog Millionaire | n/a | $292 | -42.0% | 1 | - | $292 | $92,402 | 12 | UK, USA |
| 18 | 16 | K-20: Kaijin niju menso den | M | $168 | -26.6% | 1 | - | $168 | $3,430 | 4 | Japan |
| 19 | 10 | Geu Namjaye chak 198 (Heartbreak Library) | n/a | $104 | -95.7% | 1 | -14 | $104 | $14,351 | 3 | Unknown |
| 20 | 18 | Last Chance Harvey | M | $93 | -25.0% | 1 | - | $93 | $20,692 | 7 | UK, USA |
