Company president and chief executive Mr Sittichai Leeswadtrakul said its factory was due to be ready by year-end and would start operating commercially early next year.
He said Millcon joined up with General Engineering Plc, a concrete materials maker, to build the factory to produce steel for construction and prefabricated concrete materials at Thilawa Industrial Estate.
Millcon owns 45 percent of the new asset, while General Engineering owns 45 percent and local partners 10 percent, said Mr Sittichai. Millcon invested US$7 million [K7 billion] and expects the project to break even within seven years.
He said the joint venture was the first partially owned Thai company to receive a Myanmar SEZ investment licence.
The construction materials factory is projected to earn 900 million baht [K30 billion] in revenue in 2016 and 1.2 billion by 2018, when it reaches full capacity. Millcon's total revenue is projected to reach 20 billion baht in 2016.
"Although steel demand in Myanmar is small, around 2 million tonnes last year compared with 18 million tonnes in Thailand, the demand in Myanmar doubles every year," said Mr Sittichai.
He said the factory in Myanmar would be a production base for several grades of commercial steel products.
"We will focus on downstream products because they require a smaller investment budget than upstream products and their prices are less volatile," said Mr Sittichai.
Millcon had a previous joint venture with Myanmar's Thiha Group to establish Mill Thiha, a trading company for steel and other construction materials. Mill Thiha is looking for opportunities to expand investment in construction materials and engineering services, which remains underdeveloped.
In addition, Millcon says it has an ambitious plan to invest in power generation and logistics businesses.