Is it possible to read the memory from a Holtek HT46R064B OTP(!) chip?
Every (relatively recent) MCU (OTP and erasable) I've seen has at least an optional lock bit that prevents reading the memory. The information does not seem to be in the datasheet, so it's probably in another Holtek document. Assuming they had such functionality (and even if they didn't and there was any chance of competitors reverse-engineering) it would be crazy of them not to set their programming device to configure the protection bit to prevent reading. Normally the programming is performed, it is verified, then the memory is protected (forever in the case of an OTP, only allowing bulk erase in the case of reprogrammable). 

However, the answer to your question is undoubtedly "yes". With some application of a suitable quantity of fungible assets such protection can always be broken. Maybe not by you, but someone can do it, using a variety of methods, some more invasive and expensive than others.