Some Trademark Offices do not accept to register a trademark formed of letters non pronounceable as a word because they are not enough distinctive. First at all, it is particularly the case of Thailand, where initials that are not pronounceable as a word can not be registered except if they are represented in a special manner which is distinctive enough (i.e. special font, stylized letters, devices).
Likewise, according to Vietnamese IP laws, initials which can not be pronounced as a word are not protected as a trademark, unless they are stylized to be distinctive enough or they are extensively used and recognized as a mark for a long time (i.e. notoriety trademarks such as IBM, CNN, and BBC).
Beware, the proof of such a notoriety and common knowledge falls under a hard investigation which needs the productions of large justifications. On the other side, some offices have the analogue conception, but their administrations are, in practice, less drastic. In China, South Korea, Japan and Hong Kong, to secure distinctiveness of a trademark, such trademark should include at least 3 letters.
For two-letter initials, it must be stylized or combined with words, devices In South Korea, even more, three-letter words must not be classed in alphabetical order. In conclusion and thoughtfully considered, one has to be mistrustful to automatically propose registration of initials which can not be pronounced, in particular in Asiatic countries.