Dia membaca tentang seks.

Yes. Dia is gender-neutral, so it can mean either he or she.

Malay usually does not mark gender in third-person singular pronouns the way English does. You figure it out from context.

• Dia membaca tentang seks. = He is reading about sex. / She is reading about sex.

If the context already makes the person clear, dia is perfectly normal.

Baca is the root word meaning read.
Membaca is the standard active verb form.

The prefix meN- is commonly added to roots to form an active verb in standard Malay:

• baca → membaca

So membaca is the normal textbook/written form for to read or reads/is reading.

In casual speech, especially colloquial Malay, people may sometimes use baca without the prefix, but membaca is the safer standard form for learners.

By itself, Malay does not mark tense on the verb the way English does. So membaca does not automatically tell you whether the action is present, past, or habitual.

Depending on context, Dia membaca tentang seks. could mean:

• He/She reads about sex.
• He/She is reading about sex.
• sometimes even He/She was reading about sex.

If you want to be more specific, Malay often adds time words or aspect markers:

• Dia sedang membaca tentang seks. = He/She is reading about sex.
• Dia telah membaca tentang seks. = He/She has read / had read about sex.
• Dia akan membaca tentang seks. = He/She will read about sex.

Tentang means about.

In this sentence, it introduces the topic of the reading:

• membaca tentang seks = read about sex

That is different from using seks directly as the object.
If you said Dia membaca seks, it would sound unnatural, because it would suggest seks is the thing being read directly, like a book or document title.

So when you mean read about X, tentang is the natural choice.

Yes, often you can.

• tentang = about
• mengenai = regarding / about

So:

• Dia membaca tentang seks.
• Dia membaca mengenai seks.

Both are grammatical. In many contexts, mengenai sounds a bit more formal or bookish, while tentang is very common and straightforward.

For everyday learning, tentang is an excellent default choice.

Malay usually does not use articles like English a, an, or the.

So where English says:

• about sex
• about the topic of sex

Malay can simply say:

• tentang seks

This is very normal. Malay often leaves definiteness to context rather than marking it with articles.

Mostly yes. The sentence follows a very common Malay order:

• Dia = subject
• membaca = verb
• tentang seks = prepositional phrase

So the structure is:

Subject + Verb + Prepositional Phrase

That is one reason this sentence feels quite straightforward for English speakers.

Yes, seks is a loanword, and it is pronounced roughly like English sex, usually as one syllable:

• seks

The spelling with ks at the end is normal in Malay.

This is the standard word for sex in many contexts, though depending on context you may also see related words such as:

• seksual = sexual
• hubungan seks = sexual intercourse / sexual relations

It is natural and grammatical.

However, Malay speakers might choose slightly different versions depending on what they want to emphasize:

• Dia membaca tentang seks. = general statement
• Dia sedang membaca tentang seks. = clearly happening right now
• Dia baca tentang seks. = more casual/colloquial

So your sentence is a good standard Malay sentence. It is especially suitable for learning and writing.

Not in the same way. Dia is just the normal third-person singular pronoun for a person, without gender marking.

If you want to be more respectful or formal, Malay often uses:

• the person’s title or name
• words like beliau for respected people in formal contexts

For example:

• Beliau membaca tentang seks.

But in ordinary everyday sentences, dia is completely normal.