Can employers issue a Warning Letter to foreign domestic helpers and even terminate their employment immediately?

If you browse various foreign domestic helper discussion forums or social media groups, you will find numerous complaints about the work performance and attitude of foreign domestic helpers. While there are many FDHs who perform well, grievances are usually shared only when unpleasant incidents occur. If a mistake occurs for the first time, it is advisable to communicate politely and give the FDH a chance to improve. However, can employers issue a Warning Letter to FDH and even terminate their employment immediately?