CELTA and Trinity are undoubtedly popular qualifications especially in Europe, but have far less clout in other parts of the world like Asia, for example. It really depends on where you want to teach and at what level.
Quality online TESL/TEFL Certificates are also widely accepted.
Online courses offer a great training opportunity at entry level. They can provide not only the credential you need but also the right tools to approach a new profession within a manageable amount of time and finances.
You can find online courses worth 40, 60, 80, 100 hrs. The ICAL TESL/TEFL Certificate for example is worth 100hrs. This is not equivalent to the number of hours one takes to complete a course but it is the ELT industry standard used to rate the content value of a course.
The general perception is that the less hours a course is worth the less is the value of the certificate. It’s got to be said though that employers rarely specify how many hours a TESL/TEFL Certificate should be worth. What matters to them is that you are certified by a reliable course provider.
Personally I would recommend that more than the number of hours attached to a certificate you look at the course content and the tutors’ credentials. Make sure the course requires some actual work on your part and it is not based on “Yes or No” answers or “Read This Unit and Summarize It” type of coursework. Check the reputation of the course provider.
One thing I'd say is that if you are looking at online training then you don’t need to limit yourself to what is available in your city. Check what other course providers have to offer.
As for teaching in Cambodia you might find useful this ICALwiki
fact file on Cambodia