SET-listed Siam Cement Group (SCG) will spend US$200 million to expand its investment in Cambodia from 2016-20.
The focus will be on the cement and building materials sectors, which have strong potential to grow amid the Cambodian government's policy of revving up infrastructure projects, said Kan Trakulhoon, president and chief executive of Thailand's largest industrial conglomerate.
He said SCG had already spent the equivalent of $277 million there in recent years, where the advent of the Asean Economic Community (AEC) next week is expected to trigger huge demand for cement and building materials.
"SCG sees Cambodia as one of the more interesting Asean members, with a high economic growth rate," Mr Kan said.
He said Cambodian Prime Minister Hun Sen, who met leaders of Thai and Cambodian businesses including SCG in Bangkok last Friday, pegged Cambodia's average annual growth rate at 7%.
Cambodia ranks as Thailand's eighth-largest Asean trading partner, with average annual trade valued at $3.84 billion.
Major products Thailand exports to Cambodia are refined oil, foods, beverages, cement, building materials, automobiles, and auto parts, according to Thai Commerce Ministry data.
Mr Kan said Cambodia was only one focus of SCG in Southeast Asia, as the company fully intended to continue with its planned investment in Vietnam's petrochemical industry.
Subsidiary SCG Chemicals Co recently said it would proceed with construction of a $4.5-billion petrochemical complex in that country despite the withdrawal of its partner, Doha-based Qatar Petroleum International.
Mr Kan said for overall investment prospects in Cambodia, food processing looked good, with the Cambodian government welcoming foreign investors including Thais.
With the region opening up under the AEC, tourism and property are two other interesting sectors that Thai investors should approach, he said.
TK Group president Thaveekij Jaturajarernkul, who also attended the Phnom Penh meeting, said his company had been investing in Cambodia for 25 years and was seeking more opportunities there.
His company has invested in a hotel and tourism business, property and an industrial estate in Banteay Meanchey province, which borders Thailand's Sa Kaeo province, he said.
Mr Thaveekij said the industrial estate covers 500 rai, with major production including garments, textiles and auto parts.
Many foreign investors are interested in Cambodia, which offers a variety of investment privileges to attract them, he said.
"A major Chinese investor is also talking to me about investing in my industrial estate in Banteay Meanchey and is interested in auto parts," Mr Thaveekij said.
He said other sectors such as garments and food processing were also eyeing Cambodia, as the neighbour is considered a perfect gateway to Asia-Pacific, linked to the Pacific Ocean via Vietnamese and its own seaports.
"Even Chinese investors, which used to enjoy cheap labour at home, are now taking a close look at Cambodia, where the minimum wage is substantially lower than in China," Mr Thaveekij said.
More labour-intensive businesses such as garments and textiles are moving their production bases to Cambodia from China, he added.
Chanitr Charnchainarong, chairman of the Thai-Cambodian Business Council, said it was a good sign that Cambodian leaders had attended the meeting to present their vision of how their government would promote foreign investment.
However, investors will weigh the privileges offered by the Cambodian government before making a decision, he said.
Siam Cement shares (SCC) closed Friday on the SET at 438 baht, down 14 baht, in trade worth 758 baht.