This paper presents a comparison of some different acoustic modeling strategies for under-resourced languages. When only limited speech data are available for under-resourced languages, we propose some crosslingual acoustic modeling techniques. We apply and compare these techniques in Vietnamese ASR. Since there is no pronunciation dictionary for some under-resourced languages, we investigate grapheme-based acoustic modeling. Some initialization techniques for context independent modeling and some question generation techniques for context dependent modeling are applied and compared for Khmer ASR.