Legality of Motorcycle Trailers

It may be enforced only through the driver's license.  Check on A4.   Mine (old type) says "ay kéocó trong tai den 1000 kg." which Google tells me is "The trailer has a capacity of up to 1000 kg."

@THIGV

This A4? (Link. Click to enlarge)

Further down the list it says (I think), "10 years experience". I might be wrong on that translation "Chi Goo'o" has gone to bed so I'll confirm tomorrow.

(I was indeed wrong. Thank you, yng68bld)

I'm thinking I've framed my question incorrectly. What I'm wondering is whether the small trailers which are towed behind/by a motorcycle are legal.

@Aidan in HCMC

It said expire in 10 years.  BTW, I had that same question a few years back and went to ask a traffic police man.  He said unless the trailer came with the bike legally or approved by the dept of transportation then it would be legal.  Any mickey mousing trailers would be illegal.

@yng68bld

Thank you

...I had that same question a few years back and went to ask a traffic police man.  He said unless the trailer came with the bike legally or approved by the dept of transportation then it would be legal.  Any mickey mousing trailers would be illegal. 
    -@yng68bld

Understood, entirely. I've a couple of friends here who've had their rickety home-made jobbies seized by police. Their trailers were dismantled and destroyed, and a fine was levied.

I'm thinking something along the lines of this (it will be for my dog), fitted with brake and turn-signal lights.

    @THIGV
This A4? (Link. Click to enlarge)
Further down the list it says (I think), "10 years experience". I might be wrong on that translation "Chi Goo'o" has gone to bed so I'll confirm tomorrow.
(I was indeed wrong. Thank you, yng68bld)
I'm thinking I've framed my question incorrectly. What I'm wondering is whether the small trailers which are towed behind/by a motorcycle are legal.
   

    -@Aidan in HCMC

That's a nice infographic but I can't seem to copy/paste the text into Google translate.   My other "translator" has gone to work so like you I will have to wait.   The picture of the farm tractor has me confused but may be correct.   Now that I think more about it, 1000kg does sound too big for even a large motorcycle.  I am still supposing that enforcement is through the operator's driving license and not registration of the trailer.