4148ST diode marking?
Many manufacturers that produce the same part or compatible one, use slightly different markings. For example the classic general purpose NPN transistor BC548 is often mark as C548 as well. This practice is very common. 

Your 4148ST diode is for sure the same part as or compatible with the 1N4148. 

For more detail about what the manufacturer meant by 'ST', you need to get the datasheet from that exact manufacturer and look for a section typically named 'Marking'. Some times, particularly in SMD stuff, markings in components tend to differ from the real model name they are known for, so this datasheet section becomes almost the only clue available for identifying the part and its characteristics.

In case the brand is unknown for being a cheap China fake generic clone... part,the only hope is trying to find the manufacturer they tried to clone and check its datasheet.