The film beat Mr Bean's Holiday which debuted in second place and edged out last week's number one Ghost Rider which dropped to third place.
The marketplace is also crowded with local films as at least one new domestic production opened every week last month. Currently still playing are The Sperm, Bodyguard 2, Haunting Me and Vow Out Of Death.
Opening wide on 125 prints, the big-budget $2.5m Alone is producer-distributor GMM Tai Hub's (GTH) first tentpole film of this year. It will open next in Malaysia through Golden Screen Cinemas and in Singapore via Golden Village around June.
In addition to other sales that Screendaily previously reported including France, Benelux, Brazil and Hong Kong, GTH has also secured deals with Cine Video for both Mexico and Central America, Pandasia (Taiwan) and Queen Films (Indonesia).
The picture features Thai pop singer-model-TV actress Marsha Wattanapanich as an expatriate wife living in Korea who, on her return to Thailand to visit her dying mother, has to confront her secret past - the ghost of her long dead Siamese twin.
It is directed by Parkpoom Wongpoom and Banjong Pisanthanakun whose directorial debut Shutter was the biggest Thai film in 2004. The English remake to Shutter is now in production in Tokyo with Masayuki Ochiai directing. The cast is toplined by Joshua Jackson and Rachael Taylor.