Please turn into two sentences.

ผมแอบรักเขาข้างเดียว
-> 我偷偷单恋他。
-> 我偷偷单恋她。

First, change this sentence into "我偷偷单恋他。"
Then, return to the Thai sentence, and add "我偷偷单恋她。" as a second translation.
Remember, you may add as many translations to a sentence as you need to.

Maybe "เขา" can be translated as "他们" as well?

Oh~! Thank you so much teacher~Gracias! I am so appreciated that you could help me patiently.
:-D
You are so great! How can you master so many languages!
I am currently majoring in Thai language and literature, and I love different languages all over the world and want to get acquired of them.But, their vocabularies, how to remember at least 1000 words per language and use them?
%>_<%
And I have a question here.In Thai, "ผม" is mascular. And there is no context. So I am not sure whether it is suitable to add "我偷偷单恋他。" and "我偷偷单恋他们。".

I’d like to note that you should have linked the other two sentences not to the existing Chinese one, but to the Thai sentence itself (#3274509). You can only link sentences that have the same meaning, while here you have linked a sentence with 他 to 她 and 他们. But don’t worry, I hope @cueyayotl will fix this.

I am so sorry for that, thank you very much!

@Wezel - It has been fixed. The sentences are now correctly linked.

@musclegirlxyp17 - Don't worry... Both ผม and ฉัน (or even ข่อย) will translate into only 我. The important thing in translation is to imagine a situation in which a native speaker would use the original sentence... and then imagine what you (or a native speaker in YOUR language) would say in the same situation in your native language. Of course, a slightly different situation can result in a different sentence... here on Tatoeba, you may add as many translations as you see necessary :)

For example, this sentence: "ผมแอบรักเขาข้างเดียว", if the person is male, then a Mandarin speaker will use 他; if female - 她 (same sound, but different in writing)... or if plural... then even 他们. Of course ผม with 他 implies that the speaker is 酷儿 :P

As for remembering words and expressions, practice practice practice (especially speaking/conversation). Thai is really interesting; I've learned it passively for some time (mostly Isaan dialect), I find it easy to learn because of its similarities with Khmer.

By the way, it would be very nice if you'd check "Always show transcriptions and alternative scripts" on the settings page and make sure the pinyin transcriptions of your sentences are correct. If the automatically generated one is correct, you only have to click on the "!" mark next to the pinyin. If it's wrong, you can manually edit it. This will take you some time, of course, but it will help learners a lot.

Thank you Mr.@cueyayotl , and now I understand how to add sentences on Tatoeba แล้ว:)
A Laotian student once told me, ເຈົ້າຮຽນພາສາໄທ ກໍໄດ້ສອງພາສາ, in fact we can learn at least three languages in the same time, Thai, Lao and Khmer. How charming they are! Thank you for your advice, I will practice practice and practice~!

Okay, I will do it right now, Thank you for your advice~!@tommy_san