Can a wife put a condition in the marriage contract that her husband will not take another wife?

It may be stated, but its effect differs between the schools. In the Shafi'i school (Malaysian practice), a condition that 'the husband may not marry another' is regarded as contrary to a right given by the Shariah; the condition is not binding but the marriage remains valid. The Hanbali school regards the condition as valid and binding — if the husband breaches it, the wife is entitled to dissolve the marriage. The Prophet ﷺ said that the conditions most deserving to be fulfilled are those by which you made marriage lawful. In Malaysia, a more practical route is an additional taʿliq statement recorded at registration — consult the religious affairs office or your state enactment. See conditions in the contract.