ZURICH (Reuters) - Switzerland's Holcim (>> Holcim Ltd) said on Monday it had sold its 27.5 percent stake in Thailand's second-largest cement company Siam City Cement (>> Siam City Cement PCL), in deals worth 655 million Swiss francs (458 million pounds).

Zurich-based Holcim, which plans to merge with France's Lafarge (>> LAFARGE), said 24.9 percent of Siam City Cement was acquired by an affiliate of Hong Kong-based conglomerate Jardine Matheson Holdings Ltd (>> Jardine Matheson Holdings Limited).

The remaining 2.6 percent was purchased by institutional investors, cement maker Holcim said in a statement. 

Holcim said the sale would result in a gain before taxes of approximately 365 million francs.

A source close to the deal said Holcim made the decision to sell the Siam City shares because it was unable to build up a majority stake that the company prefers to have in its holdings.

(Reporting by Joshua Franklin and Oliver Hirt; Editing by Kenneth Maxwell and Mark Potter)