Economists are putting their forecasts for Thailand under the knife after the economy contracted more than expected in the first quarter amid continued political turmoil.

"Investment has taken a big hit. Investors have really lost confidence in the country," Daniel Martin, an economist at Capital Economics, told CNBC Monday. The political situation may have become more tense, with the military declaring martial law early Tuesday. An announcement on military-run television was made to "restore order" and was not a coup, Agence France Press reported.