My 2 cents worth of my experiences with both the Mobile App (iPhone and Android) and the Web browser portal.
And I understand lots of users have had success with the Mobile App.
I tried the mobile App version a number of times and it often got into a situation of an error state and hung indefinitely at the same point.
The most common problem is once its hung there was no escape from the error state it was left in.
The messages thrown up are often cryptic and in some cases are internal module process errors that the average non IT person reads are double dutch.
Trying to contact the Website developers is like p###ing in the wind!
The mobile App version and the Web portal are not identical in their data input requirements they are slightly different if you fill in all the fields.
The mobile App version seems to be more sensitive to network related issues, user data entry syntax errors and data input delay timeouts.
The Mobile App database user input entry from the above conditions appears to have some shortcomings in recovery design; it just gives up and throws up its hands and hangs the session.
it lacks checkpoint recovery where the Mobile App backend Database server and logic should endeavour to clean up and position you back at the last viable input point in the form to continue on.
I did some network analysis from my cable modem router and found "pathpings" (network utility to measure lost network packets in detail) to the 90 day report immigration Website; it was flooded with lots of loss packets at one node in the network.
I did the same network tests over my G4 True Celular carrier and they were clean.
Now for the good news; assuming your existing visa information is entered into the Immigration Database correctly before you start the 90 Day online report.
And you successfully applied for and got the return authorization email notification for 90 day online reporting; I applied mid week and with in 1 hour had the authorization email.
1) Don't do your 90 day online reporting until you are less than 7 days out from you due date of reporting; it will not get processed outside that date and may hang?
2) Turn off PC's WiFi to your device if possible and connect to the Website visa your phone's cellular carrier's G3/G4; this minimizes network throttling, congestion and / or cable network errors.
You can hotspot from your PC into your smartphone G3/G4 (WiFi off) to get access to cellular.
You can do all this on your smartphone via the Google browser on your phone if you don't have a PC.
It's just so much easier to see overall what's going on with the form on a PC screen.
3) Go to online web portal https://extranet.immigration.go.th/fn90online/online/tm47/TM47Action.do use Google Chrome Web browser.
3) Download the User Guide; take careful note of the all the information and format required for the online form.
Fill out on a sheet of blank paper all the information required so you have the correct data input ready when you go online, review closely the required format and the content as requested in the user guide.....this is really critical!
4) Now you're ready; tick the *I have read and fully understand the above terms and conditions and agree to accept them
Now click Accept and your on your way......
I have found this method successful after so many Mobile app failures; my approval email came back within minutes along with my next 90 day report notification.
What I also found was once my Web browser session was successful, the mobile app version that was hung for weeks 24 hours later after my successful Web browser submission it was operational again where I could review my 90 reporting status through the Mobile app. (I did not use the Mobile App other then for reviewing my 90 day reporting status)
My suspicion is that there are different paths to the final 90 reporting database repository between the mobile app and Web browser session.
It looked like some cleanup processes are activated against the mobile App after midnight of the successfully Web browser portal 90 Day reporting.
Up until I had successfully reported via the Web browser portal my mobile App version was hung for many weeks; unusable.
As I said, I have found this method worked for me faultlessly; hope it helps......
Cheers and good luck