From my experience, no. You cannot get a new non-B visa until the other one has been 'closed'. This means you have paid and evidenced all required tax and SS payments and that your current employers have sent a letter stating you fulfilled your contract. There are a few documents (see attachment below), and all of these must be originals (unlike in the immigration advice attached, where it says copy, it means original) and can ONLY be supplied by your last employer. You cannot even transition to a retirement visa without 'closing' the work visa first. So, I really hope you left on good terms because there is no longer a legal requirement for your previous employer to supply these items. Here is the list from immigration as per my actual experience November-Jan in Chaeng Wattana when moving jobs. It may differ abroad...it may differ from officer to officer...