BANGKOK - A Thai shippers’ group said on Monday it expected exports to contract 4.2 percent this year, rather than the 2 percent decline it had predicted, due to weak global demand and lower oil prices. Other currencies are still weaker than the Thai baht while some manufacturers have shifted production elsewhere, the Thai National Shippers’ Council said in a statement. Exports, worth about two-thirds of the Thai economy, shrank in both 2013 and 2014 and are a big worry for an economy still struggling one year after the army took power to end political unrest. Last week, the Finance Ministry slashed its 2015 export estimate to a 4 percent decline from a rise of 0.2 percent. The central bank said it would also lower its forecast for a 1.5 percent fall.